The Teamsters, seeking to replace the union representing thousands of mechanics at United Airlines, Monday asked the National Mediation Board to set a new representation election.

Teamsters representatives said they expect an election within six weeks, and the union is confident it will prevail over the Aircraft Mechanics Fraternal Association, which currently represents more than 10,000 United mechanics.

Teamsters representatives said signatures have been collected from more than 50 percent of United mechanics who support the change in representation, which would meet legal requirements. But that level of support remains to be seen, said Steve MacFarlane, AMFA assistant national director. He said AMFA represents roughly 14,000 active and furloughed United mechanics.

The battle between the two unions takes place as thousands of United mechanics remain on furlough, and mechanic work has been outsourced, part of contract concessions that included reductions in pay and benefits.

"United Airline mechanics need a strong voice to withstand the assault on their jobs and to prevent the weakening of aviation safety and security," said Clacy Griswold, international representative for the Teamsters Airline Division.

If the Teamsters are successful, the union will poll members to determine whether they want to launch immediate contract negotiations with the airline. The current contract isn't amendable until 2009, but if union representation changes, the contract could be reopened sooner, they contend.

But a United spokeswoman responded, "All agreements remain in place when a union changes," as happened in previous similar situations.

The Teamsters also said it will fight to stop United's plans to sell its San Francisco maintenance facility and outsource its Mileage Plus program.

Kevin Giegoldt, a mechanic based at O'Hare, who supports the Teamsters, said AMFA "has done nothing to secure better wages and benefits." Supporters also said that as one of the country's biggest unions, the Teamsters has the resources to negotiate good contracts.

MacFarlane countered that as a craft union, AMFA is better able to represent the specific issue of concern to mechanics, unlike the Teamsters, which is an industrial union representing a variety of workers.

"There are tough situations in the industry today," MacFarlane said. "It's pretty typical for people to look for a white knight to save them. The Teamsters are not a white knight. There is no white knight."